Rotary switch for controlling linear motion

ABSTRACT

A rotary switch for use with storage retrieval equipment which travels linearly along a plurality of storage compartments for placement and removal of material therein. A rotatable commutator disc is mounted on a central shaft adjacent a fixed stator member. The shaft is coupled to the storage retrieval equipment for synchronous movement therewith. A plurality of contact pins corresponding to the number of storage positions, and a pair of directional control contact pins are mounted on the stator member and engage the commutator disc. A pair of arcuate conductive segments are formed on the commutator disc and engage the stator contact pins to establish an electrical circuit path across one of the conductive segments between a selected position contact pin and a directional control contact pin to select and control the movement of the storage retrieval equipment along the shortest linear path until it reaches a selected storage compartment.

United States Patent 1 1 3,766,338 Handel [451 Oct. 16,1973

[ ROTARY SWITCH FOR CONTROLLING LINEAR MOTION 7 1 ABSTRACT [76] Inventor: g g Handel North Canton A rotary switch for use with storage retrieval equipment which travels linearly along a plurality of storage [22] Filed: Oct. 6, 1972 compartments for placement and removal of material therein. A rotatable commutator disc is mounted on a [211 App! 295504 central shaft adjacent a fixed stator member. The shaft is coupled to the storage retrieval equipment for syn- [52] US. Cl. 200/11 R, 200/14 chronous movement therewith. A plurality of contact [51] Int. Cl. H01h 19/58, I-lOlh 21/78 pins corresponding to the number of storage positions, [58] Field of Search 200/11 R, 11 D, 11 DA, and a pair of directional control contact pins are 200/11 G, 11 J, 11 K, 14 mounted on the stator member and engage the commutator disc. A pair of arcuate conductive segments [56] References Cited are formed on the commutator disc and engage the UNITED STATES PATENTS stator contact pins to establish an electrical circuit 3 264 419 8/1966 Handel et a] ZOO/l1 D path across one of the conductive segments between a 3198894 8/1965 Kwg zoo/l4 selected position contact pin and a directional control 3:496:313 2/1970 Kanitzw ZOO/11 R contact pin to select and control the movement of the 2,985,726 5/1961 Handel 200/14 x Storage retrieval quipm nt along the shortest linear path until it reaches a selected storage compartment. Primary Examiner--J. R. Scott Attorney-John l-I. Bishop et a1. 5 Clalms 6 D r awmg F'gures 24 45 44 l 44 C5 SL317 5| 5 \f\ l JL, 46 4s-l- 3e 52 l?" H 62 53 4 I r l HILL t\ 7| 3 l 1 I 3 a; H 4| 39 I ll t 48 1 l 73 73 1 I A I I 72 w I I PATENTEUum 16 ms I -xii 38,98 8 POWER l fififiunmuuuuuuuu uuuu cf SUPPLY R 3 Q -|9c I f 9 I00 I I- I V v ROTARY SELECTOR SWITCH K FOR LINEAR MOTION (2o POSITIONS) FIG 6 8| 7 CCW cw 76 CCW cw A CONTROL CONTROL MOTOR I DRlVE r 79 L BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to electrical selector switches and in particular to rotary selector switches. More particularly, the invention relates to rotary selector switches which select the shortest linear path and which control the linear motion of bidirectional storage retrieval devices which travel linearly along a plurality of aligned storage compartments and stop at selected storage compartments for placement or removal of articles. I

2. Description of the Prior Art Numerous types of rotary selector switches have been developed for use with storage retrieval or filing apparatus such as shown in my previous U.S. Pat. Nos. 2,985,726 and 3,264,419, and as shown in U.S. Pat. Nos. 3,198,894 and 3,496,313. These switches are used with storage equipment orstorage retrieval mechanisms which move in a continuous orbit of travel.

These prior switches control the movement of such orbital storage equipment and retrieval mechanisms whereby the equipment and mechanisms follow the shortest path of travel. For example, assume that a pan (for discussion arbitrarily designated as pan 17), in a file of the type shown in U.S. Pat. No. 3.l98,894 having say twenty file pans, is at the file work area. Pans 18, 19, 20, 1 and 2, in that order, would move past the file work area to bring newly selected pan 3 to the work area replacing previously selected pan 17. This would be the shorter orbital path, rather than the reverse direction of moving pans 16, 15, 14, etc., past the work area to bring pan 3 to the work area.

Such continuous orbital movement of the storage pans or retrieval mechanism in either direction to arrive at a selected position is not possible in mechanisms following a linear path. The retrieval mechanism upon reaching an end position must reverse and move back along the same linear path until reaching the newly selected storage location.

Existing switches for controlling linear movement of storage retrieval mechanisms will actuate the mechanism to move always in one direction, either in ascending or descending numerical order, regardless of the existing mechanism location or the location of the newly selected storage location. The retrieval mechanism will reverse itself upon reaching the end position of the storage area if the selected storage location is not yet reached, and then will move in the opposite direction until reaching the selected location.

For example, assume that in a linearly arranged twenty position installation, a retrieval mechanism is controlled by a prior switch construction which always moves the retrieval mechanism in ascending order to arrive at a newly selected storage position. Thus, to move from an existing position 17 to a newly selected position 3, the retrieval mechanism will first move through positions 18, 19, 20 and then reverse and move back through positions l9, 18, 17, etc., to position 3. Such movement is time-consuming, especially in moving from position 4 to position 3 or the like.

One type of known switch which attempts to eliminate this wasted motion problem in linear systems is an electronic switch construction. The switch upon actuation counts the number of positions in both directions from the existing position to the selected position by electrical impulses. The switch then compares the two quantities of impulses and actuates a reversible drive motor to move the mechanism in the direction of the shortest number of impulses. Such mechanism, however, is expensive to construct and maintain.

Therefore, the need has existed for a selector switch for controlling the linear movement of storage retrieval mechanisms which is relatively inexpensive and which selects the shortest linear path and proper direction for the mechanism to move to reach a newly selected position.

SUMMARY OF THE INVENTION Objectives of the invention include providing a rotary switch for controlling linear motion of storage retrieval mechanisms whereby the switch will actuate the mechanisms to travel from their existing locations in the proper direction in order to arrive at a newly selected location with a minimum amount of linear travel and which will stop the retrieval mechanisms upon arrival at the selected position; providing a rotary switch or controlling linear motion which is equally adaptable for use with electronic and electromechanical control systems to control the linear motion of storage retrieval mechanisms; providing a rotary switch for controlling linear motion which can be constructed for use with equipment having numerous storage positions; providing a rotary switch for controlling linear motion which enables the linear spacing between adjacent storage 10- cations to be varied without effecting the proper positioning of the retrieval mechanism at a selected storage location; and providing a rotary switch for controlling linear motion which is economical to produce and maintain, and which is simple in onstruction and ope ration, which eliminates difficulties heretofore encountered, achieves the stated objectives simply and effectively, and solves problems and satisfies existing needs.

These objectives and advantages are obtained by the rotary switch for controlling the linear movement of a bidirectional storage retrieval device from any existing storage position to any desired storage position via the shortest linear path, including a fixedly mounted stator member, a rotatably mounted communicator disc cooperatively disposed adjacent the stator member and adapted to be mechanically coupled to the storage retrieval device for synchronous movement therewith, concentric inner and outer arcuate conductive seg ments carried on the commutator disc, the inner conductive segment being nested within the outer conductive segment and spaced from the outer conductive segment by a nonconductive area, the conductive seg ments each having wide and narrow arcuate portions; first and second sets of electrical contacts carried by the stator member; the first set including two directional control contacts, each contact being continuously engaged with one of the arcuate conductive segments; the second set including a plurality of contacts arcuately spaced within a portion of the stator member and corresponding to the number of storage positions, the second set of contacts adapted to be engaged with the wide portions of both conductive segments whereby a circuit path is established across one of the conductive segments between a selected contact of the second set of contacts and one of the directional control contacts which is engaged with the arcuate conductive segment engaged by the selected contact,

whereby the circuit path established controls the linear movement of the storage retrieval device until it reaches the selected storage position.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention illustrative of the best mode in which applicant has contemplated applying the principles is set forth in the following description and shown in the drawings and is 'to the storage retrieval device.

Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved rotary switch is indicated at 21 (FIG. 1) anclis shown being used to control a phonograph record storage retrieval device 22, such as used in a usual jukebox or the like. Switch 2l'includes a firstL-shaped end plate 23 mounted on a stationary base by bolts 24. A centrally positioned shaft 25'is keyed to a driven pulley 26 which is linked by belt 27 to a driven pulley 28. Pulley 28 iskeyed to a shaft 29 of a gear reduction mechanism 30, which in turn is connected to a reversible gearmotor 31. 1 I

A second belt 32 extends between pulley 28 and a larger retrieval control pulley 33. Pulley 33 is connected to a fourth pulley 34 which together with a pulley 35 moves 'aphonograph record disc storage retrieval head 36 by means ofa belt 37, to a selected record disc position.

The size ratio between pulleys 26, 28, 33, 34 and 35 is such that together with the motor speed and gear reduction mechanism they coordinate the position of record storage retrieval head 36 with the selected contact position of switch 21.

The internal structure of switch 21 (FIG. 2) includes a rotatable commutator disc 38 anda cooperating stationary stator member 39. Stator 39 serves as a mounting board for a plurality of electricalcontact pins, indicated at 40, which are urged against the bottom surface 42 of commutator disc 38 by helical expansion springs 41. Whereas actually there is a total of 22 such contact pins 40 mounted on stator member 39 in various positions, only three ofthem are shown in FIG. 2 in the interest of simplicity.

Stator 39 is mounted on corner rods 44 between the first end plate 23 and a second end plate 45, and is rigidly held in the position shown 'by spacer sleeves 46. Stator 39 is fabricated from an insulating or nonconductive material, and is generally square to match end plates 23 and 45 with a circular cutout in the center of stator 39 through which the switch shaft 25 extends. Shaft 25 is journalled for rotation in ball bearing units 47 and 48, which in turn are secured to mounting rings 4 49 and 50, respectively, which are bolted at 51 to end plates 23 and 45.

Commutator disc 38 also is formedwith a circular cutout in its center, the edges of which are securely clamped between flanges 52 integral with shaft 25 so that disc 38 rotates with the shaft. Disc 38 is fabricated from an insulating material, but in accordance with the invention its pin. contacting surface is provided with a pair of electrically conductive arcuate segments 53 and 54, as more clearly shown in FIGS. 3, 4 and 5.v

FIGS. 3-5 are taken along line 3-3, FIG. 2 and show the active or pin contacting segments 53 and 54 of commutator disc 38 in variousrotational positions, as is described more fully below in connection with an operational description of the invention. The active surface of cmmutator disc 38 includes inner andouter arcuate conductive segments 53 and 54, respectively, arranged concentric to shaft 25 and spaced from each other by a nonconductive or insulated arcuate strip 55.

Nonconductive strip 55 is a portion of the body or substrate of the disc proper, while conductive segments 53 and 54 are plated, sprayed, or otherwise deposited layers of electrically conductive material, such as copper. Conductive segments 53 and 54 have wide central portions 56 and 57, respectively, and narrower opposite end portions 58 and .59, and 60 and 61, respectively, extending circumferentially from wide portions 56 and 57. g

The cross-hatched circle in the center of disc 38 of FIGS. 3-5 represents the switch shaft 25, which is itself held out of electrical contact with the conductive surfaces of the disc by a ring-shaped area of insulation 62. Insulated area 62 is joined with the nonconductive strip' 55 by'a small section 63 of nonconductive area which separate conductive segment end portions 59 and 60.

Conductive segment 53 is nested within outer conductive segment 54 with narrow end 58 of segment 53 being adjacent wide portion 57 of segment 54, and with narrow portion 61 of segment 54 being adjacent wide portion 56 of segment 53. A radially extending position indexing nonconductive area 64, which forms a portion of nonconductive strip 55, separates the radially overlapping wide portions 56 and 57 of segments 53 and 54. Thus, circumferentially aligned and partially overlapping wide conductive portion 56 and 57 form a semicircular conductive area separated by nonconductive strip 55 which includes position indexing nonconductive area 64. v e

The small cross-hatched circles spaced in a semicircular arrangement around a portion of commutator disc 38 and labeled 1 through 20, represent the electrical contact position pins 40 that are mounted on stator 39 and urged against disc 38 by their expansion springs 41. It will be noted that these contact pins have the same respective positions throughout FIGS. 3-5. Two directional control contact pins 65 and 66, labeled CW and CCW, to denote clockwise and counterclockwise directions, also are shown as small cross-hatched circles (FIGS. 3-5) and preferably are aligned diametrically with contact position pin 11.

Pins 1-20, correspond with the twenty record storage positions indicated as 1A20A, respectively, in FIG. 1. In accordance with the invention pins 1-20 are arranged in a semicircular path, indicated by dot-dash line 67, about switch shaft 25. Pins 1-20 are contained within an area on stator 39 and are equally spaced and correspond to the spacing between storage positions 1A-20A.

Thus, for a position switch, as shown in FIGS. 3-5, pins 1-20 are spaced just slightly less than 9 apart, so that pin position 20 is slightly less than 180 from pin position 1. The width of the nonconductive position index area 64 must be less than the smallest space between any pair of adjacent position pins.

Inner and outer conductive segments 53 and 54 are continuously in contact with directional control pins 65 and 66, respectively. Inner segment 53, thus controls the CW or clockwise rotational direction of commutator disc 38, whereas outer segment 54 controls the CCW or counterclockwise rotational direction of disc 38.

Narrow ends 58 and 61 of segments 53 and 54, together with wide portions 56 and 57, maintain continuous contact with directional pins 65 and 66 throughout the rotational limits of disc 38, as seen in FIGS. 4 and 5. Whereas, narrow end portions 59 and 60, together with wide portions 56- and 57, maintain continuous contact with contact pins 1 -20.

Segment narrow end portions 59 and 60 may have a width equal to the width of wide portions 56 and 57 without effecting the operation of switch 21. End portions 59 and 60, preferably are formed narrow, as.

shown, to reduce the cost of conductive coating mate rial needed to form segments 53 and 54. Directional control pins 65 and 66, likewise, may be located at various positions on stator 39 so long as they maintain contact with segments 53 and 54, respectively.

The precise function and manner of cooperation of position pins 1-20, and directional control pins 65 and 66 with the conductive and nonconductive segments and areas of commutator disc 38 will be developed more fully below.

A usual electrical control circuit for use in conjunction with selector switch 21 and the record storage retrieval device 22, is shown in block diagram form in FIG. 6. A usual push-button keyboard 70 having at least 20 pushbuttons, indicated at 71 and labeled 1B-20B to coincide with storage positions 1A-20A, is connected to switch 21. Electrical lines indicated at 72 and labeled 1C-20C extend between pushbuttons 1B-20B and position pins 1-20. Lines 72 are connected to terminal posts 73 located at the base of the position pins 1-20 (FIG. 2).

Lines 74 and 75 connect the CW and CCW pins 65 and 66 with directional control mechanisms 76 and 77, respectively, which in turn are connected to motor drive unit 31 by lines 78 and 79, respectively. Lines 80 and 81 connect directional control mechanisms 76 and 77 to a main power supply line 82 which extends between a power supply unit 83 and motor drive unit 31.

Pushbuttons 71 have normally open contacts whereby the circuit between power supply unit 83 and motor drive unit 31 is open at keyboard 70 until a pushbutton 71 is actuated 'to move storage retrieval head 36 to the selected storage position.

Having completed the structural description of selector switch 21 of the invention and its associated control circuitry, the operation of the switch is discussed below.

Assume that. the selector switch 21 and storage retrieval head 36 are at positions 8 and 8A as indicated in FIGS. 3 and 1. In this position, position pin 8 is contacting insulated indexing area 64 between the ends of 6 wide portions 56 and 57 of conductive segments 53 and 54.

An operator depresses a pushbutton 71 on keyboard corresponding to the desired storage area or record disc location, for example, button 193. An electrical circuit is formed across keyboard 70 between power supply 83 and switch 21 through supply line 84 and line 19C. Referring to FIG. 3, the electrical circuit is formed between the energized contact pin 19 and CW pin 65 through inner conductive segment 53.

The circuit cannot be completed between pin 19 and any of the other eleven pins (20, 18 and 17-9) which are contacting segment 53 since their respective electrical connections with the main power supply line 84 are open at keyboard 70 until their respective button 71 is depressed.

The circuit is completed through line 74 to CW control mechanisms 76, and then by line 78 and power supply line 82 to main power supply 83 to energize motor drive 31 in the CW or clockwise direction (FIG. 6).

Motor drive 31 rotates pulley 28 in a clockwise direction, simultaneously moving switch connector disc 38 in a clockwise direction and moving record retrieval head 36 in a linear direction (arrow A, FIG. 1) toward position 19.

Commutator disc 38 continues to rotate in a clockwise direction until insulated index area 64 coincides with contact pin 19 (FIG. 4) which automatically breaks the electrical circuit between power supply 83 and motor drive unit 31 previously established along arcuate segment 53 between CW pin 65 and position pin 19.

Storage retrieval head 36 is synchronized with selector switch 21 through the pulley drive mechanism so that retrieval head 36 stops at record storage position 19A as disc 38 stops at contact pin position 19. Head 36 then may be automatically or manually pin position 19. Head 36 then may be automatically or manually operated by other usual control means to remove or place a record disc or the like from or into storage position 19A.

Assume the operator next selects to play the record disc in storage position 3A. Pushbutton 3B is depressed which forms an electrical circuit between power supply 83 and switch 21 through lines 84 and 3C. The electrical circuit is established between pin 3 and CCW pin 66 along conductive segment 54 to the remaining portion of the electrical circuit comprising line 75,'CCW control unit 77, and lines 79 and 83 to energize motor drive unit 31.

Motor drive 31 is driven in a counterclockwise direction by CCW control 77 rotating commutator disc 38 in a counterclockwise direction through pulley 26 and belt 27. Disc 38 continues to rotate in a counterclockwise direction from position 19 (FIG. 3) to selected position 3 (FIG. 4) until insulated area 64 coincides with contact pin 3. The electrical circuit to motor drive 31 is interrupted by area 64, stopping switch 21 at contact pin 3 and retrieval head 36 at storage position 3A.

Retrieval head 36 thus is moved directly to storage position 3A from storage position 19A (arrow B, FIG. 1) without proceeding to the end of the storage rack and reversing itself and then traveling back along the storage rack past position 19A until stopping at selected position 3A as in many prior devices.

Selector switch 21 has the further advantage of being adapted easily for use with linear storage systems in which the individual storage compartments have irregular spacings. The spacing between the various contact pins 1-20 correspond respectively, to the spacings between the storage compartments 1A-20A. Thus, pins 1-20 may be spaced irregularly arcuately long stator member 39 in direct ratio to the spacing between storage compartments lA-20A. For example, the arcuate spacing between pins 2, 3 and 4 will correspond proportionately to the linear spacing between storage compartments 2A, 3A and 4A.

Thus, pins 1-20 may have various arcuate spacings between one another corresponding to the linear spacings between storage position 1A-20A, so long as pins 1-20 are located within a 180 portion of stator 39. The arcuate length of index area 64, however, cannot be greater than the minimum spacing between any two pairs of contact pins to prevent area 64 from stopping on two such pin positions.

The particular configuration of conductive segments 53 and 54, of position pins l-20, and of CW and CCW pins 65 and 66, described above and shown in the drawings, maybe modified without departing from the concept of the invention. Switch 21 may be used for linear storage equipment having more or less than 20 storage positions by changing the number of position pins to correspond to the number of storage positions.

I Such pins, however, must remain within 180 portion of stator member 39.

Likewise, the position indicating pins may be arranged in a spiral-like path with each pin having a different radius from shaft 25. Such arrangement is desirable in some situations to reduce the formation of a common wear path on segments53 and 54 by the sliding engagement of the pin contact heads with the conductive segments. Conductive segments 53 and 54 also may have greater widths than shown and may be formed with only single narrow end portions 60 and 61.

The arcuate lengths of the wide and narrow portions of segments 53 and 54 also will vary depending upon the location of directional control pins 65 and 66. Directional control pins 65 and 66 may be located at variouspositions on stator 39 so long as they remain in contact with conductive segments 53 and 54, respectively, regardless of the rotational location of disc 38. Likewise, pins 65"and 66 must be located on opposite sides of the imaginary arcuate path 67 established by position pins l-20, and on opposite sides of nonconductive area 55. a

The minimum total arcuate length of wide portions 56 and 57 ,and index area 64 must be equal to the arcuate distance between endmost position contact pins 1 and 20. Such length is necessary to insure contact of at least one of the position pins with a wide portion of either conductive area to establish a circuit with the directional control pin contacting that particular wide portion conductive segment regardless of the rotational position of disc 38.

The electrical contacts established by the mechanical engagement of pins 1-20 and pins 65 and 66 with onductive segments 53 and 54 for controlling storage retrieval head 36 also can be achieved by photoelectric means. A commutator disc similar to disc 38 may be formed of an opaque material with segments similar to 53 and 54 being formed of translucent material. Pins 41 would be replaced by individual light sources mounted on a stator member which aligns with light-sensitive receiver means mounted on switch end plate 45.

The selection of a desired pushbutton 71 would energize the particular light source associated with the selected pushbutton which would complete an electrical circuit in a similar manner as described above for the operation of switch 21. The commutator disc would continue to rotate until the circuit is broken by breaking the light beam between the source and receiver by an opaque index area similar to area 64.

Accordingly, the rotary switch for controlling linear motion provides a simple, inexpensive switch construction which moves a bidirectional, linear motion storage retrieval device directly to a selected storage position eliminating the wasted movement heretofore encountered with prior switches as the retrieval device hunts for the selected position; and provides a switch construction which is effective and efficient in assembly, operation and use, and which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior devices, and solves problems and obtains new results in the art.

In the foregoing description, certain terms have been used for brevity, cleamess and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.

Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details of the construction shown or described.

Having now described the features, discoveries and principles of the invention, the manner in which the improved rotary switch for controlling linear motion is constructed, assembled and operated, the characteristics of the new construction, and the advantageous,

new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts, and combinations are set forth in the appended claims.

I claim:

1. A rotary selector switch for controlling the linear movement of a bidirectional storage retrieval device from any existing storage position to any desired storage position via the shortest linear path', including a fixedly mounted stator member; a rotatablymounted commutator disc cooperatively disposed adjacent the stator member and adapted to be coupled to the storage retrieval device for synchronous movement therewith; concentric inner and outer arcuate conductive segments carried on the commutator disc, said inner conductive segment being nested within the outer conductive segment and spaced from said outer conductive segment by a nonconductive area, the conductive segments each having wide and narrow arcuate portions; first and second sets of electrical contacts carried by the stator -member; spring means biasing said electrical contacts into continuous engagement with the commutator disc; the first set of contacts including two individual directional control contacts, one of said directional contacts including a plurality of individual position handling contacts arcuately spaced within a portion of the stator member and forming an imaginary path, the number of said position indicating contacts corresponding to the number of individual storage positions', the inner and outer conductive segments overlap with respect to each other, and overlap said imaginary arcuate path established by the individual storage indicating contacts; the individual position indicating contacts being engageable with one of the inner and outer conductive segments depending upon the rotational position of the commutator disc with respect to the stator member due to the overlapping of said conductive segments with respect to the imaginary arcuate path of said position indicating contacts, whereby a circuit path is established along one of the conductive segments between a selected position indicating contact and the directional control contact which is engaged with the arcuate conductive segment engaged by the selected position contact, whereby the circuit path established controls the linear movement of the storage retrieval device until it reaches the selected storage position.

2. The construction defined in claim 1 in which the non-conductive area separating the conductive segments is arcuate-shaped, in which said nonconductive area includes a radially extending index portion, and in which the arcuate width of said index portion is smaller than the arcuate spacing between any two adjacent contacts of the second set.

3. The construction defined in claim 2 in which the minimum combined arcuate length of the wide portions of the inner and outer conductive segments and the nonconductive index portion is approximately equal to the total arcuate spacing between the endmost contacts of the second set of contacts.

4. The construction defined in claim 1 in which the wide portions of the inner and outer conductive segments have a sufficient radial width to engage both their respective directional control contacts and the second set of contacts throughout the rotational limits of the commutator disc.

5. The construction defined in claim 1 in which the electrical contacts of the second set are equally spaced arcuately from each other, and in which said contacts are arranged in a semi-circular configuration. 

1. A rotary selector switch for controlling the linear movement of a bidirectional storage retrieval device from any existing storage position to any desired storage position via the shortest linear path, including a fixedly mounted stator member; a rotatably mounted commutator disc cooperatively disposed adjacent the stator member and adapted to be coupled to the storage retrieval device for synchronous movement therewith; concentric inner and outer arcuate conductive segments carried on the commutator disc, said inner conductive segment being nested within the outer conductive segment and spaced from said outer conductive segment by a nonconductive area, the conductive segments each having wide and narrow arcuate portions; first and second sets of electrical contacts carried by the stator -member; spring means biasing said electrical contacts into continuous engagement with the commutator disc; the first set of contacts including two individual directional control contacts, one of said directional contacts being continuously engaged with the inner arcuate conductive segment and the other of said directional contacts being continuously engaged with the outer conductive arcuate segment; the second set of contacts including a plurality of individual position handling contacts arcuately spaced within a 180* portion of the stator member and forming an imaginary path, the number of said position indicating contacts corresponding to the number of individual storage positions; the inner and outer conductive segments overlap with respect to each other, and overlap said imaginary arcuate path established by the individual storage indicating contacts; the individual position indicating contacts being engageable with one of the inner and outer conductive segments depending upon the rotational position of the commutator disc with respect to the stator member due to the overlapping of said conductive segments with respect to the imaginary arcuate path of said position indicating contacts, whereby a circuit path is established along one of the conductive segments between a selected position indicating contact and the directional control contact which is engaged with the arcuate conductive segment engaged by the selected position contact, whereby the circuit path established controls the linear movement of the storage retrieval device until it reaches the selected storage position.
 2. The construction defined in claim 1 in which the non-conductive area separating the conductive segments is arcuate-shaped, in which said nonconductive area includes a radially extending index portion, and in which the arcuate width of said index portion is smaller than the arcuate spacing between any two adjacent contacts of the second set.
 3. The construction defined in claim 2 in which the minimum combined arcuate length of the wide portions of the inner and outer conductive segments and the nonconductive index portion is approximately equal to the total arcuate spacing between the endmost contacts of the second set of contacts.
 4. The construction defined in claim 1 in which the wide portions of the inner and outer conductive segments have a sufficient radial width to engage both their respective directional control contacts and the second set of contacts throughout the rotational limits of the commutator disc.
 5. The construction defined in claim 1 in which the electrical contacts of the second set are equally spaced arcuately from each other, and in which said contacts are arranged in a semi-circular configuration. 